Under intense pressure from Washington, Egyptian security forces arrested hundreds of protesters around the U.S. Embassy in Cairo on Saturday, as political leaders struggled to deal with the fallout caused by the week of unrest.

Across the region, the anti-American demonstrations that convulsed cities in many parts of the Islamic world last week subsided at least temporarily, a fragile calm taking hold a day after violent and sometimes deadly demonstrations at U.S. and Western installations spread to almost 20 countries.

In Cairo, where the protests against a crude video denigrating Islam began Tuesday, security forces expanded the fortifications around the U.S. Embassy. By midday Saturday, they had cleared the streets around the complex.

Hisham Qandil, Egypt's prime minister, said Saturday that he had visited the U.S. Embassy to express his support and told the BBC's Arabic news channel that it was regrettable and wrong that so many blamed the U.S. government for a video to which it had no connection.

But he also called for the West to "strike a balance between freedom of expression and to maintain respect for other people's beliefs."

Even as the violence abated, al Qaeda's branch in Yemen urged its followers to "expel the embassies of America from the lands of the Muslims" and praised Tuesday's killing of the U.S. ambassador to Libya, J. Christopher Stevens.

The violence raised questions about political instability in Egypt, Tunisia and other Middle Eastern countries where newfound freedoms have given way to an absence of authority.

On Saturday, President Obama condemned the violence but also reached out to Muslims.

"We stand for religious freedom," he said in his weekly radio address. "And we reject the denigration of any religion - including Islam. Yet there is never any justification for violence."

The State Department said Saturday that it was evacuating all family members and nonemergency staff members from the embassies in Tunisia and Sudan, citing security concerns.